Filter diagnostics and prognostics

ABSTRACT

Various systems and methods are provided for a lubricant filter. In one example, a method for a lubricant filter comprises indicating a condition of the filter based on a difference between a measured pressure differential and an expected pressure differential during select conditions in which all lubricant pumped by a pump upstream of the filter flows into the filter.

FIELD

The field of the disclosure relates to lubricant filters.

BACKGROUND AND SUMMARY

Lubrication systems are used in internal combustion engines to lubricateand reduce friction within moving components in the engine, therebyincreasing the operational life of the components and the engine. Forexample, pistons, crankshafts, bearings, etc., may be lubricated withoil by a lubrication circuit provided in an engine. The lubricationcircuit may include a filter configured to reduce particulates fromlubricant that may otherwise interfere with component lubrication. Asthe filter ages, particulates accumulate therein, eventually reaching aprevalence at which replacement of the filter is recommended.

U.S. Pat. No. 6,553,290 discloses methods of identifying clogging in alubricant or fluid filter. Specifically, clogging in an engine oilfilter is detected by measuring the pressure drop across the filter.

The inventors herein have recognized an issue with the approachidentified above. Typical oil circuits provide one or more bypass orpressure relief valves that enable oil to bypass an oil filter at orabove a threshold oil pressure. During conditions in which one or moreof these valves are open, at least a portion of oil flowing through anoil circuit bypasses the filter. As such, pressure drops across thefilter measured during these conditions are not fully indicative offilter clogging. Use of filter pressure drops during these conditionsmay lead to inaccurate identification of filter clogging, which mayprompt unnecessary replacement of the filter.

One approach that at least partially addresses the above issues includesa method for a lubricant filter comprising indicating a condition of thefilter based on a difference between a measured pressure differentialand an expected pressure differential during select conditions in whichall lubricant pumped by a pump upstream of the filter flows into thefilter.

In a more specific example, the condition is one of a nominal conditionand a degraded condition

In another example, the expected pressure differential is determined asa product of a lubricant flow rate and a lubricant viscosity.

In yet another example, the lubricant filter is configured to filterlubricant in a lubrication circuit including the pump, a filter bypassvalve, and a pressure relief valve, and during the select conditions anoutlet pressure of the pump is limited to less than one or both ofrespective setpoints of the filter bypass valve and the pressure reliefvalve.

In this way, pressure differentials across a lubricant filter may beaccurately correlated to nominal or degraded filter conditions, whichmay reduce excessively early filter replacement, in turn reducing costsand hazardous waste issues associated with filter replacement. Thus, thetechnical result is achieved by these actions.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure. Finally, the above explanation does not admit any ofthe information or problems were well known.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example oil circuit of an internal combustion engine.

FIG. 2 shows another example oil circuit of an internal combustionengine.

FIG. 3 is a schematic diagram showing an example engine.

FIGS. 4A-B show a flowchart illustrating a diagnostic routine for afilter in an oil circuit.

FIG. 5 shows a flowchart illustrating a prognostic routine for a filterin an oil circuit.

DETAILED DESCRIPTION

Various systems and methods are provided for a lubricant filter. In oneexample, a method for a lubricant filter comprises indicating acondition of the filter based on a difference between a measuredpressure differential and an expected pressure differential duringselect conditions in which all lubricant pumped by a pump upstream ofthe filter flows into the filter. FIG. 1 shows an example oil circuit ofan internal combustion engine, FIG. 2 shows another example oil circuitof an internal combustion engine, FIG. 3 is a schematic diagram showingan example engine, FIGS. 4A-B show a flowchart illustrating a diagnosticroutine for a filter in an oil circuit, and FIG. 5 shows a flowchartillustrating a prognostic routine for a filter in an oil circuit. Theengine of FIG. 3 also includes a controller configured to carry out themethods depicted in FIGS. 4A-5.

FIG. 1 schematically shows an example oil circuit 1 of an internalcombustion engine 50. Details regarding an example engine which may beengine 50 are provided below with reference to FIG. 3. Oil circuit 1comprises a cylinder head oil circuit 1 a, a cylinder block oil circuit1 b, and an oil sump 1 c which enables the storage and distribution ofengine oil.

To enable the circulation of engine oil through oil circuit 1, an oilpump 2 is in fluidic communication with oil sump 1 c via a suction line3. Oil pump 2 may thus drive oil flow by suctioning oil from oil sump 1c through suction line 3 and pumping the suctioned oil to componentsdownstream of the oil pump. In some examples, suction line 3 may besized to provide a desired flow rate of oil to oil pump 2. Moreover, oilpump 2 may be configured to provide various desired aspects of oil flow,such as a desired oil pressure or a desired oil volume flow rate asdescribed in further detail below.

In some implementations, oil pump 2 is mechanically driven by engine50—for example, the oil pump may be coupled to a crankshaft (e.g.,crankshaft 40 of FIG. 3) of the engine. In this case, determining thespeed of oil pump 2 may include determining the speed of engine 50, asthe pump speed may be directly proportional to the engine speed.Embodiments in which oil pump 2 is electrically driven are within thescope of this disclosure, however. Oil pump 2 may be a positive or fixeddisplacement pump, in which case the oil pump may be of various suitabletypes, including but not limited to a gear pump, a trochoid pump, a vanepump, a plunger pump, etc. In other examples, oil pump 2 may be avariable displacement pump. In the case that oil pump 2 is a variabledisplacement pump, the oil pump may be controlled on the basis of adesired outlet pressure and may include a mechanical-hydraulic feedbackmechanism to alter its displacement so as to achieve the desired outletpressure. In other examples, oil pump 2 may be controlled on the basisof a desired displacement and may include a mechanism to providepressure feedback such as an electronic oil pressure sensor.

Positioned downstream of oil pump 2 is a pressure relief valve 22, whichis in fluidic communication with the outlet of the oil pump at a firstend and with oil sump 1 c at a second end opposite the first end.Pressure relief valve 22 may be configured to divert oil flow away fromdownstream components and back to oil sump 1 c when the outlet pressureof oil pump 2 exceeds a threshold pressure, thereby limiting the oilpressure in oil circuit 1. Pressure relief valve 22 may be a check valvethat requires a given pressure to open, for example. It will beappreciated that pressure relief valve 22 may assume other locationswithin oil circuit 1 without departing from the scope of thisdisclosure. FIG. 2 illustrates one such alternative placement of apressure relief valve within an oil circuit.

A variety of lubricant-receiving components 5 are positioned along asupply line 4, which generally provides a fluidic pathway along whichoil may flow to such lubricant-receiving components. Lubricant-receivingcomponents 5 may include at least two bearings (e.g., camshaft bearings,crankshaft bearings, etc.), camshaft mountings, and/or crankshaftmountings. Lubricant-receiving components 5 may include additionallubricant-receiving components not shown in FIG. 1, including but notlimited to a connecting rod, balancer shaft, a piston head, etc. Thepiston head may be sprayed with oil via a nozzle, for example, and thenozzle may be positioned below the piston head. Lubricant-receivingcomponents 5 may further include a hydraulically actuated camshaftadjuster or other valve gear components, for hydraulic valve clearanceadjustment.

As shown in FIG. 1, supply line 4 is in fluidic communication with theoutlet of oil pump 2 and the inlet of a lubricant filter 6, and pressurerelief valve 22 is in fluidic communication with this portion of thesupply line interposed between the oil pump and filter. Supply line 4feeds to filter 6, which is positioned downstream of oil pump 2. Filter6 may be any suitable filter for removing particulates from oil in oilcircuit 1. For example, filter 6 may be a cartridge that removesparticulates that are greater than a pore size of the filter. As anotherexample, filter 6 may be magnetic and thus may sequester ferromagneticparticles. As yet another example, filter 6 may trap particulates viasedimentation, centrifugal forces, or another method for removingparticulates from oil.

Filter 6 includes a filter bypass valve 6 a configured to allow oil tobypass the filter responsive to the oil pressure in oil circuit 1exceeding a relief pressure setpoint at which the bypass valve isconfigured to open. Filter bypass valve 6 a may prevent the formation ofunacceptably high pressure differentials across filter 6 that mightotherwise degrade the filter, and provides a bypass around the filterfor scenarios in which the filter is clogged. Oil bypassing filter 6(e.g., when filter bypass valve 6 a is open) may be referred to as“unfiltered” oil.

The friction exhibited by lubricant-receiving components 5 (e.g.,crankshaft bearings) may vary as a function of the viscosity andconsequently the temperature of the oil supplied thereto. Such frictionmay also affect fuel consumption by engine 50. Accordingly, oil circuit1 includes an oil cooler/heater 7 configured to at least partiallycontrol the temperature of oil in the oil circuit and to reduce frictionlosses in lubricant-receiving components 5. As shown in FIG. 1, oilcooler/heater 7 is positioned downstream of filter 6 and is in fluidiccommunication with the filter via supply line 4. Oil cooler/heater 7 mayselectively remove/add heat from oil flowing through oil circuit 1—forexample, it would not remove heat during warm up of engine 50. In someexamples, oil cooler/heater 7 may remove heat from oil via air coolingand/or liquid cooling. In one specific example, oil cooler/heater 7 mayutilize coolant from an engine cooling circuit to remove heat from oil.It will be appreciated that the location of oil cooler/heater 7 may beadjusted without departing from the scope of this disclosure. Forexample, in alternative embodiments oil cooler/heater 7 may bepositioned upstream of filter 6.

Following flow through oil cooler/heater 7, engine oil may then flow toa main oil gallery 8 via supply line 4. In the depicted configuration,main oil gallery 8 forms part of cylinder block oil circuit 1 b. Assuch, main oil gallery 8 may be arranged in a cylinder block of engine50. A plurality of ducts 8 a branch off from main oil gallery 8 and leadto five main bearings 9 a of a crankshaft of engine 50 (e.g., crankshaft40 of FIG. 3) and four big-end bearings 9 to thereby lubricate thebearings. A main supply duct, which may be aligned along thelongitudinal axis of the crankshaft, may form at least a portion of themain oil gallery 8. The main supply duct may be arranged above or belowthe crankshaft in a crankcase or it may be integrated into thecrankshaft. In some examples, oil may be supplied to the bearingsnon-continuously to increase the pressure in the oil circuit 1 andspecifically in the main oil gallery 8.

Supply line 4 fluidly couples cylinder block oil circuit 1 b to cylinderhead oil circuit 1 a, thereby enabling the supply of oil to variouslubricant-receiving components 5 included in the cylinder head oilcircuit, such as bearings 10 a and 11 a respectively associated with twocamshaft mountings 10 and 11. Supply ducts branching off from main oilgallery 8 may provide oil to camshaft mountings 10 and 11, for example.In some examples the supply ducts may traverse a cylinder block ofengine 50, and when the camshaft is an overhead camshaft, the supplyducts may traverse a cylinder head of the engine.

As, in the configuration depicted in FIG. 1, oil flows from oil sump 1 cfirst to cylinder block oil circuit 1 b and then to cylinder head oilcircuit 1 a, oil may be first supplied to a cylinder block of engine 50and then to a cylinder head of the engine. Consequently, oil may beinitially heated during flow through the cylinder block and then furtherheated during subsequent flow through the cylinder head. Such aconfiguration may enable rapid heating of oil in oil circuit 1, whichmay be desired following restart of engine 50, for example. It will beappreciated, however, that alternative configurations are possiblewithout departing from the scope of this disclosure. For example, inother embodiments oil may be first supplied to the cylinder head ofengine 50 and subsequently to the cylinder block of the engine. In yetother embodiments, separate supply lines may be provided for thecylinder head and block (e.g., for circuits 1 a and 1 b) in a parallelconfiguration such that both the cylinder head and block can besimultaneously fed oil if desired.

Oil circuit 1 further includes return lines 13 branching off from atleast one of the two camshaft mountings 10 and 11 and from main oilgallery 8 to enable the return of oil to oil sump 1 c following flowthrough lubrication-receiving components 5. The return of oil to oilsump 1 c via return lines 13 may be driven by gravity, for example. Insome embodiments, return lines 13 may be positioned in low-temperatureareas and/or adjacent to any liquid cooling provided for the cylinderhead and/or cylinder block of engine 50. In this way, the likelihood ofthe oil in the return lines 13 increasing beyond a desired operatingtemperature is decreased; excessive temperatures of oil in return lines13 can adversely affect various characteristics of the return oil suchas lubricating quality, and can cause more rapid aging of the returnoil.

Since the operation of filter 6 significantly affects oil supply tolubricant-receiving components 5, and thus operation of engine 50,assessment of the condition of the filter may be desired. For example,knowledge of whether or not filter 6 is significantly clogged and/orwhether filter bypass valve 6 a is opening may be desired. Further,knowledge of the remaining operational life of filter 6 may be desired,for example in an attempt to provide a vehicle operator an estimate ofthe number of miles left until replacement of the filter is recommended.Accordingly, oil circuit 1 includes a differential pressure sensor 14configured to provide an indication of the pressure differential acrossfilter 6 by sensing oil pressure upstream and downstream of the filter.Indications of the pressure differential across filter 6 may be used toperform both diagnostics on the filter—e.g., assessments of the currentcondition of the filter such as whether or not it is clogged—andprognostics on the filter—e.g., the remaining operational life of thefilter. As shown in FIG. 1, differential pressure sensor 14 providesindications of the differential filter pressure (e.g., as a singledifferential pressure signal or as two signals respectively indicatingpressure upstream and downstream of the filter) to a controller 12,described below with reference to FIG. 3. In some examples, differentialpressure sensor 14 may sense oil pressure upstream of the inlet offilter bypass valve 6 a.

To perform diagnostics and prognostics on filter 6, the measuredpressure differential across the filter as sensed by differentialpressure sensor 14 may be compared to an expected pressure differentialacross the filter. Diagnostics may conclude, for example, that filter 6is partially clogged (e.g., not fully clogged or unclogged) if themeasured pressure differential is greater than the expected pressuredifferential. Partial clogging of filter 6 may indicate that someportion of the operational life of the filter remains and thatreplacement of the filter is not yet recommended, for example.Alternatively or additionally, diagnostics may conclude that filter 6 isfully clogged if the measured pressure differential is greater than theexpected pressure differential and near (e.g., within 10%) the reliefpressure setpoint of filter bypass valve 6 a at which the bypass valveis configured to open. Alternatively or additionally, diagnostics mayconclude that the relief pressure setpoint of filter bypass valve 6 amay be excessive if the measured pressure differential is substantiallygreater than the relief pressure setpoint—e.g., by 10% or more.Alternatively or additionally, diagnostics may make no conclusion as tothe condition of filter 6 or filter bypass valve 6 a if the expectedpressure differential is near the relief pressure setpoint of the filterbypass valve.

In some examples, the expected pressure differential across filter 6 maybe determined based on the flow rate of oil in oil circuit 1 (e.g., atthe inlet of the filter) and the viscosity of the oil. TheHagen-Poiseuille equation provides a non-limiting example illustratinghow an expected pressure drop (e.g., differential) across afluid-receiving device can be determined based on flow rate andviscosity; the equation may assume the following form:ΔP=(8*μ*L*Q)/(π*r^4), where ΔP is the expected pressure drop, μ is thedynamic viscosity, L is the length of the cylindrical pipe in whichfluid flows, Q is the volumetric flow rate of the fluid, π is themathematical constant pi, and r is the radius of the cylindrical pipe.As can be seen from this equation, the expected pressure drop isdirectly proportional to both the fluid flow rate and the fluidviscosity. The Hagen-Poiseuille equation particularly yields thepressure drop for a long cylindrical pipe, which may not be thegeometric configuration assumed by filter 6. However, lubricant flowthrough filter 6 may be in the laminar regime; thus, the pressure dropacross filter 6 may be directly proportional to both lubricant flow anddynamic viscosity.

Determination of the expected pressure differential across filter 6 mayinclude assessing one or more aspects of operation of oil pump 2, as oilflow rate in oil circuit 1 may be a function of operation of the oilpump. In some examples, the oil flow rate in oil circuit 1 (e.g., at theinlet of filter 6) may be determined based on the speed of oil pump 2.Determination of the speed of oil pump 2 may include determining thespeed of engine 50 for embodiments in which the oil pump is mechanicallydriven by the engine, as the pump speed may be directly proportional tothe engine speed. In some examples, determination of the oil flow ratemay further include determining the displacement of oil pump 2. Forembodiments in which oil pump 2 is a positive displacement pump, thepump displacement may be known, stored in, and retrieved from controller12, for example. For embodiments in which oil pump 2 is a variabledisplacement pump, the pump displacement may be determined via apositional feedback mechanism in the pump. Alternatively (e.g., if thepositional feedback mechanism is not provided), the pump displacementmay be inferred based on one or more known displacements—for example,the pump displacement corresponding to the minimum output (e.g., flowrate, pressure) of the pump and the pump displacement corresponding tothe maximum output of the pump may be used to infer (e.g., interpolate)the pump displacement corresponding to an intermediate output betweenthe minimum and maximum outputs.

When either pressure relief valve 22 or filter bypass valve 6 a opens asa result of oil pressure in oil circuit 1 exceeding a respective reliefpressure setpoint, filter 6 does not receive the entirety of oil flowpumped by oil pump 2—at least a portion of oil flow bypasses the filtervia the filter bypass valve and/or returns to oil sump 1 c beforereaching the filter via the pressure relief valve. The oil flow ratethrough filter 6 may thus be unknown without measuring or inferring oilflow through pressure relief valve 22 and/or filter bypass valve 6 a.Lacking knowledge of the oil flow rate through filter 6, the expectedpressure drop across the filter may be unable to be accuratelydetermined, preventing the performance of diagnostics and/or prognosticson the filter that utilize expected pressure drop. Thus, in someembodiments diagnostics and/or prognostics that use the expectedpressure drop across filter 6 may be determined only under selectconditions in which neither of pressure relief valve 22 and filterbypass valve 6 a is open and oil flow through oil circuit 1 can beentirely attributed to flow through the filter. Put another way,diagnostics and/or prognostics may be only performed on filter 6 of oilcircuit 1 if the oil pressure (e.g., outlet pressure of oil pump 2) inthe oil circuit does not exceed the respective relief pressure setpointsof pressure relief valve 22 and filter bypass valve 6 a. Under theseconditions, the flow rate produced by oil pump 2 may be substantiallyequal to the flow rate through filter 6, and as such the filter flowrate may be parameterized by the oil pump flow rate.

Oil viscosity, which as described above may be used along with oil flowrate to determine the expected pressure differential across filter 6,may be inferred from oil temperature, as oil viscosity may correlatewith oil temperature for some types of oil. The temperature of oil inoil circuit 1 may be determined via an oil temperature sensor (notshown), or alternatively inferred from readings output by one or moresensors of engine 50 described below with reference to FIG. 3, such asan engine coolant temperature sensor. Determination of oil viscosity mayalternatively or additionally include retrieving a predetermined oilviscosity of oil intended for engine 50 from controller 12. Oil havingthe predetermined oil viscosity may have been installed in engine 50upon manufacture, for example. Deviation from the predetermined oilviscosity—or an expected oil viscosity in general—may be detected basedon operation of oil pump 2. For example, an expected oil pressure may bedetermined based on engine speed and engine coolant temperature andcompared to a measured oil pressure (e.g., measured via differentialpressure sensor 14 or a non-differential pressure sensor not shown inFIG. 1); deviation from the expected oil pressure may indicate deviationfrom an expected oil viscosity. In some examples, a detected deviationmay be used to adjust a predetermined oil viscosity.

In some implementations, a suitable data structure (e.g., lookup table)may store a plurality of expected pressure differentials across filter6, enabling retrieval of expected pressure differentials by accessingthe data structure with one or more suitable indices. For embodiments inwhich oil pump 2 is a positive displacement pump, the indices mayinclude engine speed and oil temperature, as these parameters maydetermine oil flow rate and oil viscosity and thus an expected pressuredifferential. For embodiments in which oil pump 2 is a variabledisplacement pump, the indices may include engine speed, oiltemperature, and pump displacement. The data structure may be stored incontroller 12, for example.

Diagnostics performed on filter 6 may account for conditions in which arelatively high pressure differential across the filter is expected andnot indicative of degraded filter or filter bypass valve operation. Forexample, a relatively high pressure differential across filter 6 may beconsidered nominal if the product of oil flow rate in oil circuit 1 andthe viscosity of the oil is relatively high. Such conditions may occurduring cold start of engine 50, for example, due to the high viscosityexhibited by some engine oils at relatively cold temperatures. In somescenarios, such conditions may also cause filter bypass valve 6 a toopen, whose opening may be considered normal under such conditions.

Known conditions in which a relatively high pressure differential acrossfilter 6 is expected may also be utilized to recognize degradation(e.g., clogging) of the filter and potentially recommend replacement ofthe filter to a vehicle operator. For example, opening of filter bypassvalve 6 a may be expected during cold engine start and consideredindicative of normal filter operation as described above. Thisexpectation may be used such that opening of filter bypass valve 6 aduring conditions other than cold start is recognized as an indicationthat filter 6 has degraded—e.g., reached the end of its operationallife. Various actions may be performed responsive to determining thatfilter 6 has reached the end of its operational life, including one ormore of indicating filter end-of-life via a dashboard indicator, settinga diagnostic code in an engine controller, etc. The results ofprognostics described herein may also be indicated via such means; forexample, a prognostic indicating that a portion of the operational lifeof filter 6 remains may be followed by indicating the remainingoperational life to a vehicle operator (e.g., miles left to replacementvia a dashboard indicator). Alternatively or additionally, a timer maybe set in an engine controller such that, upon expiration of the timer,the vehicle operator is notified of extinction of the remainingoperational life (as determined by the prognostic or a subsequentdiagnostic/prognostic) and/or engine operation is modified to compensatefor filter degradation.

Opening of filter bypass valve 6 a may also be utilized to performdiagnostics on the filter bypass valve itself. One such diagnostic mayinclude assessing the relief pressure setpoint at which filter bypassvalve 6 a is configured to open. In this diagnostic, the actual pressurerelief setpoint may be determined based on output from differentialpressure sensor 14 responsive to opening of filter bypass valve 6 a, asthe differential pressure sensor will read the actual setpoint of thebypass valve when the bypass valve is open. The relief pressure setpointread by differential pressure sensor 14 under these conditions (e.g.,during opening of filter bypass valve 6 a, which may be detected viaoutput from a position switch described below) may be compared to one orboth of an upper threshold and a lower threshold. If the read pressurerelief setpoint exceeds the upper threshold, the diagnostic may concludethat the setpoint is faulted high, which may allow excessively largepressure differentials to form across filter 6 that can potentiallydegrade filter operation. It may then be indicated (e.g., via dashboardindicators, setting a diagnostic code, etc.) that the setpoint isfaulted high if exceeding the upper threshold. If the read reliefpressure setpoint falls below the lower threshold, the diagnostic mayconclude that the setpoint is faulted low, which may increase theproportion of unfiltered oil passed to engine 50, which can reduce theoperational life of the engine. It may then be indicated that thesetpoint is faulted low if falling below the lower threshold. Thisfilter bypass valve diagnostic may thus be performed only during selectconditions in which filter bypass valve 6 a is open, and the oil pumpedfrom the outlet of pump 2 does not entirely flow through filter 6.

Prognostics performed on filter 6 may assess the difference between themeasured pressure differential across the filter and the relief pressuresetpoint of filter bypass valve 6 a. For example, an estimation of theremaining operational life of filter 6 may be determined based on thisdifference. As a specific non-limiting example, an estimation of thedistance (e.g., miles) remaining until filter replacement is recommendedmay be determined by computing the absolute value of the differencebetween the measured pressure differential and the relief pressuresetpoint and multiplying the absolute value of this difference by aconstant relating pressure to distance.

FIG. 1 illustrates the potential inclusion of a position switch 16 whichmay be used to perform prognostics on filter 6. Position switch 16 maybe coupled to filter bypass valve 6 a such that the position switchoutputs a signal each time the filter bypass valve opens. In thisconfiguration, an estimate of the remaining operational life of filter 6may be determined based on the frequency of filter bypass valve opening.As a specific non-limiting example, an estimation of the distanceremaining until filter replacement is recommended may be determined bycomputing the inverse frequency of filter bypass valve opening andmultiplying this inverse frequency by a constant relating frequency todistance. Alternatively or additionally, changes in the filter bypassvalve opening frequency over time may be monitored to assess thecondition of filter 6.

It will be appreciated that oil circuit 1 is provided as an example andthat various modifications to the oil circuit are possible withoutdeparting from the scope of this disclosure. For example, the number oflubricant-receiving components 5 and the relative positioning ofcomponents in oil circuit 1 are non-limiting. In some embodiments,position switch 16 may be omitted from oil circuit 1. Moreover, whiledescribed with reference to engine oil, it will be appreciated that theapproaches described herein may apply to fluid circuits that circulateother types of lubricants and fluids. Still further, embodiments arepossible in which diagnostics and prognostics are performed for filter 6using a non-differential pressure sensor—e.g., a sensor that outputs asingle pressure reading. In this example, the measured pressuredifferential across filter 6 may be determined based on the differencebetween the single pressure reading and the commanded pressure accordingto which oil pump 2 may be driven.

FIG. 2 schematically shows an example oil circuit 1′ of an internalcombustion engine 50′. It is sought to explain the differences betweenFIGS. 1 and 2, and as such, like parts are numbered similarly. As can beseen in FIG. 2, oil circuit 1′ exhibits a configuration similar to thatof oil circuit 1 of FIG. 1. Unlike oil circuit 1 of FIG. 1, however, oilcircuit 1′ includes a pressure relief valve 22′ positioned downstream offilter 6 and upstream of oil cooler/heater 7. In this configuration, theoutlet of an oil pump 2′ feeds directly into a junction joining theinlet of filter 6 to filter bypass valve 6 a, whereas in oil circuit 1of FIG. 1 pressure relief valve 22 is interposed between these twolocations.

In some embodiments, oil pump 2′ may specifically be a variabledisplacement pump and not a fixed displacement pump. In this example,the operation of oil pump 2′ may cooperate with the placement ofpressure relief valve 22′ to enable oil flow through oil circuit 1′ tobe controlled on the basis of volume flow rate, alternatively or inaddition to on the basis of pressure. More specifically, oil pump 2′ maybe controlled such that the outlet pressure of the oil pump does notexceed the relief pressure setpoint of filter bypass valve 6 a (andoptionally such that the outlet pressure of the oil pump does not exceedthe relief pressure setpoint of pressure relief valve 22′), preventingopening of the filter bypass valve and optionally opening of thepressure relief valve. Under these select conditions, all of the oilpumped from the outlet of oil pump 2′ flows through filter 6 and notthrough pressure relief valve 22′ or filter bypass valve 6 a. Withsufficient knowledge of the operation of oil pump 2′, the oil flow ratethrough filter 6 can be accurately determined, enabling accuratedetermination of an expected pressure drop across the filter andcorrelation of some types of pressure drops across the filter withfilter clogging. Use of a variable displacement pump may enable the oilpressure in oil circuit 1′ to be maintained below the relief pressuresetpoint of filter bypass valve 6 a (and optionally the relief pressuresetpoint of pressure relief valve 22′) at a higher frequency as comparedto use of a fixed displacement pump. This may consequently increase theproportion of engine/vehicle operation in which diagnostics and/orprognostics may be performed on filter 6, as oil flow rate and thusexpected pressure drop may be definitively determined. Embodiments arecontemplated, however, in which oil pump 2′ is a fixed displacementpump, in which case diagnostics and/or prognostics that evaluate anexpected pressure differential across filter 6 may be performed onlyunder select conditions under which oil flow goes entirely through thefilter and does not bypass the filter through filter bypass valve 6 a.

With the outlet pressure of oil pump 2′ limited such that all oil flowpumped from the outlet of the oil pump can be attributed to flow throughfilter 6, the expected pressure differential across the filter may bedetermined and compared to the measured pressure differential across thefilter as sensed by differential pressure sensor 14 in a manner similarto that described above. For example, the expected pressure differentialacross filter 6 may be determined as a function of oil flow rate throughoil circuit 1 and oil viscosity. As described above, oil flow rate maybe determined based on the speed of oil pump 2 (e.g., which may bedetermined based on engine speed for embodiments in which the oil pumpis mechanically driven by engine 50) and the displacement of the oilpump for embodiments in which the oil pump is a variable displacementpump, while oil viscosity may be inferred from oil temperature, whichmay or may not include assessing a predetermined oil viscosity.

As with oil circuit 1 of FIG. 1, diagnostics may conclude that filter 6of oil circuit 1′ is partially clogged (e.g., not fully clogged orunclogged) if the measured pressure differential across the filter isgreater than the expected pressure differential. Alternatively oradditionally, diagnostics may conclude that filter 6 is fully clogged ifthe measured pressure differential is greater than the expected pressuredifferential and near (e.g., within 10%) the relief pressure setpoint offilter bypass valve 6 a at which the bypass valve is configured to open.Alternatively or additionally, diagnostics may conclude that the reliefpressure setpoint of filter bypass valve 6 a may be excessive if themeasured pressure differential is substantially greater than the reliefpressure setpoint—e.g., by 10% or more. Alternatively or additionally,diagnostics may make no conclusion as to the condition of filter 6 orfilter bypass valve 6 a if the expected pressure differential is nearthe relief pressure setpoint of the filter bypass valve. As describedabove, high pressure differentials across filter 6 may be expected andconsidered indicative of nominal, non-degraded operation of the filterunder some conditions such as engine cold start.

FIG. 3 is a schematic diagram showing an example engine 100, which maybe included in a propulsion system of an automobile. In someembodiments, engine 100 may be engine 50 of FIG. 1 or engine 50′ of FIG.2. Although not shown in FIG. 3, engine 100 may be lubricated by asuitable lubrication system such as oil circuit 1 of FIG. 1 or oilcircuit 1′ of FIG. 2.

The engine 100 is shown with four cylinders 30. However, other numbersof cylinders may be used in accordance with the current disclosure.Engine 100 may be controlled at least partially by a control systemincluding controller 12, and by input from a vehicle operator 132 via aninput device 130. In this example, input device 130 includes anaccelerator pedal and a pedal position sensor 134 for generating aproportional pedal position signal PP. Each combustion chamber (e.g.,cylinder) 30 of engine 100 may include combustion chamber walls with apiston (not shown) positioned therein. The pistons may be coupled to acrankshaft 40 so that reciprocating motion of the piston is translatedinto rotational motion of the crankshaft. Crankshaft 40 may be coupledto at least one drive wheel of a vehicle via an intermediatetransmission system (not shown). Further, a starter motor may be coupledto crankshaft 40 via a flywheel to enable a starting operation of engine100.

Combustion chambers 30 may receive intake air from intake manifold 44via intake passage 42 and may exhaust combustion gasses via exhaustpassage 48. Intake manifold 44 and exhaust manifold 46 can selectivelycommunicate with combustion chamber 30 via respective intake valves andexhaust valves (not shown). In some embodiments, combustion chamber 30may include two or more intake valves and/or two or more exhaust valves.

Fuel injectors 51 are shown coupled directly to combustion chamber 30for injecting fuel directly therein in proportion to the pulse width ofsignal FPW received from controller 12. In this manner, fuel injector 51provides what is known as direct injection of fuel into combustionchamber 30. The fuel injector may be mounted in the side of thecombustion chamber or in the top of the combustion chamber, for example.Fuel may be delivered to fuel injector 51 by a fuel system (not shown)including a fuel tank, a fuel pump, and a fuel rail. In someembodiments, combustion chambers 30 may alternatively, or additionally,include a fuel injector arranged in intake manifold 44 in aconfiguration that provides what is known as port injection of fuel intothe intake port upstream from each combustion chamber 30.

Intake passage 42 may include throttle 21 and 23 having throttle plates20 and 24, respectively. In this particular example, the position ofthrottle plates 20 and 24 may be varied by controller 12 via signalsprovided to an actuator included with throttles 21 and 23. In oneexample, the actuators may be electric actuators (e.g., electricmotors), a configuration that is commonly referred to as electronicthrottle control (ETC). In this manner, throttles 21 and 23 may beoperated to vary the intake air provided to combustion chamber 30 amongother engine cylinders. The position of throttle plates 20 and 24 may beprovided to controller 12 by throttle position signal TP. Intake passage42 may further include a mass air flow sensor 120, a manifold airpressure sensor 122, and a throttle inlet pressure sensor 123 forproviding respective signals MAF (mass airflow) MAP (manifold airpressure) to controller 12.

Exhaust passage 48 may receive exhaust gasses from cylinders 30. Exhaustgas sensor 128 is shown coupled to exhaust passage 48 upstream ofturbine 62 and emission control device 78. Sensor 128 may be selectedfrom among various suitable sensors for providing an indication ofexhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO(universal or wide-range exhaust gas oxygen), a two-state oxygen sensoror EGO, a NOx, HC, or CO sensor, for example. Alternatively, sensor 128may be positioned downstream of turbine 62. Emission control device 78may be a three way catalyst (TWC), NOx trap, various other emissioncontrol devices, or combinations thereof.

Exhaust temperature may be measured by one or more temperature sensors(not shown) located in exhaust passage 48. Alternatively, exhausttemperature may be inferred based on engine operating conditions such asspeed, load, AFR, spark retard, etc.

Controller 12 is shown in FIG. 3 as a microcomputer, includingmicroprocessor unit 102, input/output ports 104, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 106 in this particular example, random access memory 108,keep alive memory 110, and a data bus. Controller 12 may receive varioussignals from sensors coupled to engine 100, in addition to those signalspreviously discussed, including measurement of inducted mass air flow(MAF) from mass air flow sensor 120; engine coolant temperature (ECT)from temperature sensor 112, shown schematically in one location withinthe engine 100; a profile ignition pickup signal (PIP) from Hall effectsensor 118 (or other type) coupled to crankshaft 40; the throttleposition (TP) from a throttle position sensor, as discussed; andabsolute manifold pressure signal, MAP, from sensor 122, as discussed.Engine speed signal, RPM, may be generated by controller 12 from signalPIP. Manifold pressure signal MAP from a manifold pressure sensor may beused to provide an indication of vacuum, or pressure, in the intakemanifold 44. Note that various combinations of the above sensors may beused, such as a MAF sensor without a MAP sensor, or vice versa. Duringstoichiometric operation, the MAP sensor can give an indication ofengine torque. Further, this sensor, along with the detected enginespeed, can provide an estimate of charge (including air) inducted intothe cylinder. In one example, sensor 118, which is also used as anengine speed sensor, may produce a predetermined number of equallyspaced pulses every revolution of the crankshaft 40. In some examples,storage medium read-only memory 106 may be programmed with computerreadable data representing instructions executable by processor 102 forperforming the methods described below as well as other variants thatare anticipated but not specifically listed.

Engine 100 may further include a compression device such as aturbocharger or supercharger including at least a compressor 60 arrangedalong intake manifold 44. For a turbocharger, compressor 60 may be atleast partially driven by a turbine 62, via, for example a shaft, orother coupling arrangement. The turbine 62 may be arranged along exhaustpassage 48 and communicate with exhaust gasses flowing therethrough.Various arrangements may be provided to drive the compressor. For asupercharger, compressor 60 may be at least partially driven by theengine and/or an electric machine, and may not include a turbine. Thus,the amount of compression provided to one or more cylinders of theengine via a turbocharger or supercharger may be varied by controller12. In some cases, the turbine 62 may drive, for example, an electricgenerator 64, to provide power to a battery 66 via a turbo driver 68.Power from the battery 66 may then be used to drive the compressor 60via a motor 70. Further, a sensor 123 may be disposed in intake manifold44 for providing a BOOST signal to controller 12.

Further, exhaust passage 48 may include wastegate 26 for divertingexhaust gas away from turbine 62. In some embodiments, wastegate 26 maybe a multi-staged wastegate, such as a two-staged wastegate with a firststage configured to control boost pressure and a second stage configuredto increase heat flux to emission control device 78. Wastegate 26 may beoperated with an actuator 150, which may be an electric actuator such asan electric motor, for example, though pneumatic actuators are alsocontemplated. Intake passage 42 may include a compressor bypass valve 27configured to divert intake air around compressor 60. Wastegate 26and/or compressor bypass valve 27 may be controlled by controller 12 viaactuators (e.g., actuator 150) to be opened when a lower boost pressureis desired, for example.

Intake passage 42 may further include charge air cooler (CAC) 80 (e.g.,an intercooler) to decrease the temperature of the turbocharged orsupercharged intake gasses. In some embodiments, charge air cooler 80may be an air to air heat exchanger. In other embodiments, charge aircooler 80 may be an air to liquid heat exchanger.

Further, in the disclosed embodiments, an exhaust gas recirculation(EGR) system may route a desired portion of exhaust gas from exhaustpassage 48 to intake passage 42 via EGR passage 140. The amount of EGRprovided to intake passage 42 may be varied by controller 12 via EGRvalve 142. Further, an EGR sensor (not shown) may be arranged within theEGR passage and may provide an indication of one or more of pressure,temperature, and concentration of the exhaust gas. Alternatively, theEGR may be controlled through a calculated value based on signals fromthe MAF sensor (upstream), MAP (intake manifold), MAT (manifold gastemperature) and the crank speed sensor. Further, the EGR may becontrolled based on an exhaust O₂ sensor and/or an intake oxygen sensor(intake manifold). Under some conditions, the EGR system may be used toregulate the temperature of the air and fuel mixture within thecombustion chamber. FIG. 3 shows a high pressure EGR system where EGR isrouted from upstream of a turbine of a turbocharger to downstream of acompressor of a turbocharger. In other embodiments, the engine mayadditionally or alternatively include a low pressure EGR system whereEGR is routed from downstream of a turbine of a turbocharger to upstreamof a compressor of the turbocharger.

FIGS. 4A-B show a flowchart illustrating a diagnostic routine 400 for afilter in an oil circuit. Routine 400 may be applied to one or both ofoil circuits 1 and 1′ of FIGS. 1 and 2, respectively, to assess thecondition of filter 6, for example. Further, routine 400 may be storedas instructions on computer-readable storage (e.g., memory of controller12 of FIGS. 1-3) and executed by a processor (e.g., CPU 102 ofcontroller 12). It will be appreciated that aspects of routine 400 mayvary depending on the configuration of the oil circuit and/or pump towhich the method is applied, as described below. Moreover, routine 400may be employed to lubrication circuits that circulate lubricants otherthan oil.

At 402 of routine 400, it is determined whether oil flowing through theoil circuit is flowing entirely through the filter and is not bypassingthe filter. Oil bypassing the filter may do so by flowing around thefilter via a filter bypass valve (e.g., filter bypass valve 6 a of FIGS.1 and 2) and/or via a pressure relief valve (e.g., pressure reliefvalves 22, 22′ of FIGS. 1 and 2, respectively) positioned upstream ofthe filter, for example. A determination that oil flows entirely throughthe filter, and does not bypass the filter, enables assessment of thecondition of the filter on the basis of an expected pressuredifferential across the filter. Determination of the expected pressuredifferential may involve accurately assessing the flow rate of oilthrough the filter, which in some examples can only be facilitated ifoil does not bypass the filter. As such, in some examples the conditionof the filter may be assessed on the basis of an expected pressuredifferential cross the filter only during select conditions in which oilpumped from the outlet of a pump flows entirely into an inlet of thefilter and does not bypass the filter, for example via a filter bypassvalve configured to bypass oil around the filter for oil pressuresgreater than or equal to a setpoint of the bypass valve, or a pressurerelief valve which may be interposed between the pump and the filter.

Determining whether oil flowing through the oil circuit is flowingentirely through the filter and is not bypassing the filter at 402 mayinclude, at 404, determining whether engine speed is greater than athreshold speed. Since the outlet pressure of a pump driving oil flowthrough the oil circuit may be proportional to engine speed (e.g., dueto being mechanically driven by the engine), engine speeds above thethreshold speed may correlate to pump outlet pressures that exceed therelief setpoint of one or both of the filter bypass valve and thepressure relief valve. In other words, one or both of the filter bypassvalve and the pressure relief valve may open at engine speeds above thethreshold speed, in which case oil does not flow entirely through thefilter. Engine speed may be determined based on output from a sensorsuch as sensor 118 of FIG. 3 as described above. For embodiments inwhich the pump is a fixed displacement pump, mitigation of pump outletpressures that cause opening of one or both of the filter bypass valveand the pressure relief valve, and thus oil bypass around the filter,may not be possible. For embodiments in which the pump is a variabledisplacement pump, however, pump outlet pressure may be limited so thatoil does not bypass the filter by adjusting the displacement of thepump, even at engine speeds above the threshold speed. If it isdetermined at 404 that the engine speed exceeds the threshold speed(YES), routine 400 proceeds to 406. If it is determined at 404 that theengine speed is less than or equal to the threshold speed (NO), routine400 proceeds to 408.

At 406 of routine 400, it is determined whether or not the pump is afixed displacement pump. An engine controller may store the type of pumpemployed in the oil circuit; as such, determining whether or not thepump is a fixed displacement pump may include retrieving the pump typefrom the engine controller. If it is determined that the pump is a fixeddisplacement pump (YES), routine 400 returns to 404. In this way,assessment of the filter condition may be suppressed for conditions inwhich oil bypasses the filter and pump operation cannot be adjusted todrive oil flow entirely through the filter. If it is determined that thepump is not a fixed displacement pump (NO), routine 400 proceeds to 408.In this case, the pump may be a variable displacement pump.

At 408 of routine 400, the displacement of the pump may be optionallyadjusted, for embodiments in which the pump is a variable displacementpump, so that the outlet pressure of the pump is less than the setpointsof the filter bypass valve and the pressure relief valve. Forembodiments in which the pressure relief valve is positioned downstreamof the filter, however, pump displacement may be modified to limit pumpoutlet pressure below the filter bypass valve setpoint, and not to limitpump outlet pressure below the pressure relief valve setpoint. It willbe appreciated that, depending on the configuration of the variabledisplacement pump, either adjustments to the pump displacement oradjustments to the pump outlet pressure may be commanded (e.g., by anengine controller such as controller 12 of FIGS. 1-3). For embodimentsin which adjustments to the pump outlet pressure are commanded, the pumpdisplacement may adjusted by commanding adjustments to the pump outletpressure, which may include limiting the pump outlet pressure below thesetpoint of the filter bypass valve and the setpoint of the pressurerelief valve if positioned upstream of the filter. For embodiments inwhich adjustments to the pump displacement are commanded, a suitabledata structure (e.g., lookup table) or transfer function may be employedto determine a corresponding change in pump outlet pressure for a givenadjustment in pump displacement. The determined change in pump outletpressure may be compared to one or both of the setpoints of the filterbypass valve and the pressure relief valve to determine a suitableadjustment to displacement. Pump displacement may be decreased as enginespeed increases, for example, to maintain pump outlet pressure belowexcessive pressures that cause oil bypass around the filter. It will beappreciated that, in some scenarios, the pump displacement may not bemodified even if it was determined at 404 that engine speed exceeds thethreshold speed, as the corresponding pump outlet pressure for theunadjusted pump displacement may not cause oil to bypass the filter.

It will be appreciated that other actions may be performed as part ofdetermining whether oil flowing through the oil circuit is flowingentirely through the filter and is not bypassing the filter at 402,alternatively or in addition to those described above. For example, apressure sensor positioned upstream of the filter, filter bypass valve,and pressure relief valve may be used to determine whether the pumpoutlet pressure is high enough to cause one or both of the filter bypassand pressure relief valves to open. With reference to FIGS. 1 and 2, theupstream pressure sensed by differential pressure sensor 14 may be usedfor embodiments in which the sensor senses oil pressure upstream of theinlet of filter bypass valve 6 a and pressure relief valve 22 (or valve22′). If an oil pressure that is likely to cause opening of one or bothof the filter bypass valve and the pressure relief valve is detected,the condition of the filter may not be assessed according to routine 400for fixed displacement pump embodiments, whereas pump operation (e.g.,outlet pressure, displacement) may be modified for variable displacementembodiments. In other embodiments, a pressure switch may be used todirectly detect opening of the filter bypass valve and the pressurerelief valve, if coupled thereto.

At 410 of routine 400, an expected pressure differential (AP) across thefilter is determined. The expected pressure differential may bedetermined as a product of oil flow rate through the oil circuit and theviscosity of the oil in the oil circuit. As such, determining theexpected pressure differential may include, at 412, determining the oilflow rate based on pump operation. For embodiments in which the pump isa fixed displacement pump, the oil flow rate may be determined based onpump speed (e.g., engine speed). For embodiments in which the pump is avariable displacement pump, the oil flow rate may be determined based onpump speed and pump displacement. Determining the expected pressuredifferential may further include, at 414, determining the oil viscositybased on oil temperature, which as described above may be measured orinferred.

At 415 it is determined whether the expected pressure differentialdetermined at 410 is within a threshold range of the relief pressuresetpoint of the filter bypass valve. If it is determined that theexpected pressure differential is not within the threshold range of thefilter bypass valve setpoint (NO), routine 400 proceeds to 416. If it isdetermined that the expected pressure differential is within thethreshold range of the filter bypass valve setpoint (YES), routine 400proceeds to 417 where no conclusion is made—e.g., no assessment as tothe condition of the filter is made. Following 417, routine 400 ends.Routine 400 may be controlled responsive to the expected pressuredifferential and the threshold range around the filter bypass valvesetpoint in this way so as to prevent erroneous conclusions that mayotherwise be reached when the expected pressure differential is withinthe threshold range of the filter bypass valve setpoint. For example, ifthe expected pressure differential is within the threshold range of thefilter bypass valve setpoint, pressure differentials measured across thefilter under these conditions, and that are close to the expectedpressure differential, may be interpreted as an indication that thefilter is operating normally and that the filter bypass valve is notopen. In actuality, however, the filter bypass valve may have been open,for example if the measured pressure differential exceeds the filterbypass valve setpoint (e.g., by 2%). Various suitable threshold rangesmay be used. As a non-limiting example, the threshold range may be 10%about the filter bypass valve setpoint, such that expected pressuredifferentials that are not 10% or closer to the setpoint lead to furtherexecution of routine 400, and expected pressure differentials that are10% or closer to the setpoint lead to termination of the routine.

At 416 of routine 400, the pressure differential across the filter ismeasured. The pressure differential across the filter may be measuredvia a differential pressure sensor such as sensor 14 of FIGS. 1 and 2,for example. Alternative approaches are possible, however, in which anon-differential pressure sensor reading is compared to a commandedpressure to determine the pressure differential across the filter.

Turning now to FIG. 4B, at 418 of routine 400, it is determined whetherthe measured pressure differential exceeds the expected pressuredifferential. If it is determined that the measured pressuredifferential exceeds the expected pressure differential (YES), routine400 proceeds to 420. If it is determined that the measured pressuredifferential does not exceed (e.g., is less than or equal to) theexpected pressure differential (NO), routine 400 proceeds to 422 whereno conclusion is made—e.g., no assessment as to the condition to thefilter is made. However, in some approaches, reaching no conclusion at422 may be considered indicative of nominal filter operation—e.g., thatthe filter is operating normally and not in a degraded mode (e.g.,clogged). Routine 400 may optionally proceed to 423 where the nominalcondition of the filter may be indicated to a vehicle operator, whichmay include providing an estimate of the remaining operational life ofthe filter to the vehicle operator. A method 500 illustrated in FIG. 5may be used to estimate the remaining operational life of the filter andprovide an indication thereof to the vehicle operator, for example. Itwill be appreciated that, under some operating conditions, a relativelyhigh pressure differential across the filter may be expected (e.g.,during engine cold start); detection of a relatively high pressuredifferential across the filter under these conditions may be consideredindicative of a nominal (e.g., non-degraded) condition of the filter.

At 420 of routine 400, it is determined whether the measured pressuredifferential is near the relief pressure setpoint of the filter bypassvalve. The setpoint of the filter bypass valve (and potentially thesetpoint of the pressure relief valve) may be stored in, and retrievedfrom, an engine controller, or, alternatively, may be determined bysensing the pressure at which the valve opens. Pressure differentialsmay be considered to be near the relief pressure setpoint if within 5%,for example. If it is determined that the measured pressure differentialis near the relief pressure setpoint of the filter bypass valve (YES),routine 400 proceeds to 424. If it is determined that the measuredpressure differential is not near (e.g., not within 5% of) the reliefpressure setpoint of the filter bypass valve (NO), routine 400 proceedsto 432.

At 424 of routine 400, it is determined that the filter is clogged. Insome examples, an extent of clogging may be inferred, for example as apercentage of total clogging, based on the nearness of the measuredpressure differential to the filter bypass valve setpoint—for example, agreater extent of clogging may be inferred the closer the measuredpressure differential is to the filter bypass valve setpoint. As such,in some examples, partial clogging of the filter may be determined at424, while in other examples, full clogging (e.g., 100%) may bedetermined at 424. In some implementations, a relatively greater extentof clogging may be determined at 424 as compared to the determinationperformed at 438, described below. Clogging of the filter may beconsidered to correspond to a (e.g., partially) degraded condition ofthe filter.

Various actions may be optionally performed following 424. For example,at 426, a vehicle operator may be optionally warned of filter clogging,which in some examples may include providing an estimate of the extentof clogging. At 428 of routine 400, a diagnostic code indicating filterdegradation may be optionally set in an engine controller. At 430 ofroutine 400, engine operation may be optionally modified to compensatefor filter degradation, which may include limiting engine output, forexample. More specifically, engine operation may be modified so thatengine operating conditions under which oil pressure and flow rate aremaximum are avoided. Such modification to engine operation may includelimiting engine speed (e.g., to speeds below 1500 RPM) for embodimentsin which oil pressure and flow rate are a function of engine speed. Insome examples, the engine speed limit may vary with oil viscosity suchthat a higher limit is employed for higher engine speeds (where oil isless viscous) and a relatively lower limit is employed for relativelylower engine speeds (where oil is more viscous). Following 430, routine400 ends.

If it was determined at 420 that the measured pressure differential isnot near the filter bypass valve setpoint (NO), routine 400 proceeds to432 where it is determined whether the measured pressure differential issubstantially greater than the filter bypass valve setpoint. A measuredpressure differential may be considered to be substantially greater thanthe filter bypass valve setpoint if greater than the setpoint by 15% ormore, for example. If it is determined that the measured pressuredifferential is substantially greater than the filter bypass valvesetpoint (YES), routine 400 proceeds to 434 where it is determined thatthe filter bypass valve setpoint is faulted high. A fault in the filterbypass valve setpoint may be considered to correspond to a degradedcondition of the filter. This may be followed by various optionalactions, including, at 436, warning the vehicle operator of a filterbypass fault. Following 436, routine 400 ends.

If it is determined at 432 that the measured pressure differential isnot substantially greater than the filter bypass valve setpoint (NO),routine 400 proceeds to 438 where it is determined that the filter ispartially clogged. In some examples, partial clogging may include anylevel of clogging between fully unclogged (e.g., 0% clogging) and fullyclogged (e.g., 100% clogging, in which case oil may be unable to flowthrough the filter under any operating conditions). In other examples,partial clogging determined at 438 may be less than partial or fullclogging that may otherwise have been determined at 424. Partialclogging may be considered to correspond to a degraded condition of thefilter. Here, the measured pressure differential is greater than theexpected pressure differential but not near or substantially greaterthan the filter bypass valve setpoint. Various optional actions mayfollow 438, including, at 440, warning the vehicle operator of partialfilter clogging, which in some examples may include providing anestimate of the extent of clogging and/or providing an estimate of theremaining operational life (e.g., in terms of a distance in miles,kilometers) of the filter. Following 440, routine 400 ends.

It will be appreciated that various aspects of routine 400 may bemodified without departing from the scope of this disclosure. Forexample, the oil circuit to which routine 400 is applied may include twoor more pressure relief valves upstream of a filter, in which case thecondition of the filter may be assessed based on an expected pressuredifferential across the filter only when oil flows entirely through thefilter and does not bypass the filter through any of the pressure reliefvalves upstream of the filter.

FIG. 5 shows a flowchart illustrating a prognostic routine 500 for afilter in an oil circuit. Routine 500 may be applied to one or both ofoil circuits 1 and 1′ of FIGS. 1 and 2, respectively, for example.Further, routine 500 may be stored as instructions on computer-readablestorage (e.g., memory of controller 12 of FIGS. 1-3) and executed by aprocessor (e.g., CPU 102 of controller 12). Moreover, routine 500 may beemployed to lubrication circuits that circulate lubricants other thanoil.

At 502 of routine 500, the remaining operational life of the filter isestimated. The remaining operational life of the filter may be estimatedbased on, at 504, the difference between the measured pressuredifferential (ΔP) across the filter and the expected pressuredifferential across the filter. As described above, the pressuredifferential across the filter may be measured via a differentialpressure sensor such as sensor 14 of FIGS. 1 and 2, while the expectedpressure differential may be based on the oil flow rate and viscosity inthe oil circuit. In some examples, the remaining operational life may beproportional to the difference between the measured and expectedpressure differentials, such that a relatively small difference may leadto an estimation of a relatively short remaining operational life, whilea relatively large difference may lead to an estimation of a relativelylong remaining operational life. Alternatively or additionally, theremaining operational life of the filter may be estimated based on, at506, the frequency of filter bypass valve (e.g., valve 22 or 22′ ofFIGS. 1 and 2, respectively) opening. Opening of the filter bypass valvemay be detected via output from a position switch (e.g., switch 16 ofFIGS. 1 and 2) coupled to the bypass valve, for example. A relativelyhigher frequency of filter bypass valve opening may lead to anestimation of a relatively shorter remaining operational life, while arelatively lesser frequency of filter bypass valve opening may lead toan estimation of a relatively longer operational life, for example.

At 508 of routine 500, the remaining operational life of the filterestimated at 502 is indicated to a vehicle operator. The remainingoperational life of the filter may be indicated to the vehicle operatorin various suitable manners, such as via a dashboard indicator.Alternatively or additionally, the remaining operational life of thefilter may be displayed to the vehicle operator, for example via anin-vehicle display, which may be positioned proximate a center consoleof the vehicle. In some examples, the remaining operational life may beindicated to the vehicle operator in the form of a distance that, whentraveled by the vehicle, exhausts the estimated remaining operationallife of the filter. At this point, replacement of the filter may berecommended (e.g., due to clogging).

At 510 of routine 500, replacement of the filter may be optionallyscheduled based on the remaining operational life of the filterestimated at 502. For example, the replacement may be scheduled in anengine controller (e.g., controller 12 of FIGS. 1-3) in terms of adistance that, when traveled by the vehicle, prompts recommendation offilter replacement, which may be indicated to the vehicle operator.Following 510, routine 500 ends.

Thus, as shown and described, routines 400 and 500, of FIGS. 4 and 5,respectively, may be used to accurately assess the condition of a filterin a lubrication circuit on a significantly granular level. In someparticular examples, the remaining operational life of the filter may bedetermined and optionally indicated to a vehicle operator, enablingexcessively early replacement of the filter, which may reduce costs andhazardous waste issues associated with lubricant filter replacement. Thediagnostics and/or prognostics described herein may be carried out onlyduring select conditions in which, for example, one or more valves thatenable lubricant bypass around a filter are maintained fully closed bylimiting an outlet pressure of a pump upstream of the filter and the oneor more valves.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method for a lubricant filter,comprising: indicating a condition of the filter based on a differencebetween a measured pressure differential output from a differentialpressure sensor and an expected pressure differential during selectconditions in which all lubricant pumped by a pump upstream of thefilter flows into the filter, wherein a degraded condition of the filtercorresponding to a fault of a filter bypass valve setpoint is indicatedif the measured pressure differential is greater than the expectedpressure differential and is substantially greater than the filterbypass valve setpoint.
 2. The method of claim 1, wherein the conditionis one of a nominal condition and the degraded condition.
 3. The methodof claim 1, wherein the expected pressure differential is determined asa product of a lubricant flow rate and a lubricant viscosity.
 4. Themethod of claim 3, wherein the lubricant flow rate is determined basedon one or both of a speed and a displacement of the pump.
 5. The methodof claim 3, wherein the lubricant viscosity is determined based onlubricant temperature.
 6. The method of claim 1, further comprisingfiltering lubricant in a lubrication circuit via the pump, a filterbypass valve, and a pressure relief valve, and wherein during the selectconditions, an outlet pressure of the pump is limited to less than oneor both of respective setpoints of the filter bypass valve and thepressure relief valve.
 7. The method of claim 6, wherein the outletpressure of the pump is limited by adjusting a displacement of the pump.8. The method of claim 1, wherein, during the select conditions, enginespeed is less than a threshold engine speed.
 9. The method of claim 1,wherein the degraded condition of the filter corresponding to partialclogging of the filter is indicated via one or more of a diagnostic codeand a dashboard indicator if the measured pressure differential isgreater than the expected pressure differential but is neither near norsubstantially greater than the filter bypass valve setpoint.
 10. Themethod of claim 1, wherein the degraded condition of the filtercorresponding to full clogging of the filter is indicated via one ormore of a diagnostic code and a dashboard indicator if the measuredpressure differential is greater than the expected pressure differentialand is near the filter bypass valve setpoint.
 11. The method of claim 1,wherein a nominal condition of the filter is indicated via one or moreof a diagnostic code and a dashboard indicator if the measured pressuredifferential is not greater than the expected pressure differential. 12.The method of claim 1, further comprising displaying a remainingoperational life of the filter based on one of the difference betweenthe measured pressure differential and the expected pressuredifferential, and a frequency of filter bypass valve opening.
 13. Themethod of claim 12, wherein displaying the remaining operational life ofthe filter as a distance that, when traveled by a vehicle, promptsrecommendation of filter replacement includes estimating a relativelyshorter remaining operational life for a relatively higher frequency offilter bypass valve opening, and wherein displaying the remainingoperational life of the filter includes estimating a relatively longerremaining operational life of the filter for a relatively lesserfrequency of filter bypass valve opening.
 14. A method for a lubricantfilter, comprising: indicating a condition of the filter based on adifference between a measured pressure differential sensed by adifferential pressure sensor and an expected pressure differentialduring select conditions in which all lubricant pumped by a pumpupstream of the filter flows into the filter, displaying a remainingoperational life of the filter based on one of the difference betweenthe measured pressure differential and the expected pressuredifferential, and a frequency of filter bypass valve opening, whereindisplaying the remaining operational life of the filter includesestimating a relatively shorter remaining operational life for arelatively higher frequency of filter bypass valve opening, and whereindisplaying the remaining operational life of the filter includesestimating a relatively longer remaining operational life of the filterfor a relatively lesser frequency of filter bypass valve opening.